Hexavalent chromium, which is produced as a by-product of numerous industrial processes, is a serious environmental pollutant. It is toxic, mutagenic and highly pestilential since it causes lung carcinoma in humans. This hexavalent form is soluble in water and easily absorbed by the soil, leading to the contamination of the ground water supplies. Thus conversion of this soluble form to insoluble form has become mandatory. Chemical methods used for this reduction process are highly expensive for large-scale decontamination and have damaging consequences. Hence the development of Bioremediation is highly desirable. Bacteria are capable of reducing chromium from the hexavalent (toxic) to the trivalent form (disarmed form) via the Cr (v) intermediate form, but few improvements at the cellular as well as enzymatic level are required to make them efficient agents of chromate bioremediation. This reduction is basically done by Bacillus species and using the enzyme reductase.
Reduction depends on the type and concentration of the organic substrate used for bacterial growth. Diphenyl carbazide method using UV Visible Spectrophotometer is used for the estimation of Hexavalent chromium. X-ray absorption spectroscopy later confirmed the reduction mechanism in bacteria. Addition of same substrate has seen to increase the rate of reduction of chromium and synchronously also the growth of bacteria.
In our presentation, we will be dealing with the isolation of hexavalent chromium reducing bacteria from contaminated Environment, its biochemical characterization, the ability of the bacterium to reduce hexavalent chromium, Optimization of temperature and pH for maximum Chromium reduction (general kinetics of the reduction mechanism) and the localization of the chromium Reducing activity. We will also be dealing with the 3D structure change during the reduction process. This could be a sustainable solution as bacteria are widely distributed in the environment and screening of reductase enzyme producing strains is not a demanding task. Since bacterial growth takes place at a very rapid rate it is possible to produce reductase enzyme in 72 hours with trace amount of chromate and nutrients. Industrial symbiosis could be a feasible option and hence the wastewater from the food industries could be used as a source of bacterial growth and reductase production. Since there are a large number of industries that emit wastewater without treating them, this technique would enhance the reduction of toxic compounds. This is done both in a direct and indirect manner, thus enabling the maintenance of ecological balance without causing any harm to the species.
